Diarrheal diseases and wasting are major manifestations of advanced infection by the human immunodeficiency virus. The present study will determine the importance of diarrheal illness in HIV infection in Zambia, determine the causes and will examine the sequential microbiological, immunological and clinical aspects that lead to chronic diarrhea and slim disease. It is anticipated that information will be gained that could help us prevent enteric infection by environmental, behavioral or chemoprophylactic/chemotherapeutic intervention. The specific aims of the present project are: 1. To characterize the microbiology and clinical features of acute enteric infection in HIV seropositive and seronegative patients and to determine their relationship to the development of chronic diarrhea. 2. To determine the contribution of enteric microbial infection to chronic diarrhea and the wasting syndrome (Slim Disease) in HIV-infected adults. 3. To show the relationship of pathogen-specific diarrhea and degree of immunosuppression in HIV-infected patients with chronic diarrhea. 4. To develop clinical therapeutic trials in adults with chronic diarrhea once information is available on etiology. A case control study of adult and pediatric patients (HIV-positive versus HIV-negative) at the University Teaxching Hospital, Lusaka, with acute and chronic diarrhea will be carried out with a comparison of clinical features of disease, enteric etiologic agents, and risk factors for HIV acquisition. In addition to the study of clinical and microbiologic features of chronic disease and wasting, four areas will be studied as possible explanations for weight loss and malnutrition in HIV infected persons: altered food intake; intestinal dysfunction; metabolic alteration; and micronutrient deficiency. Intestinal dysfunction patterns will be sought using a physiologic and anatomic orientation. During yeats 3-5 of the present study clinical therapeutic trials will be carried out in adult patients with chronic diarrhea which will be based on the etiologic information learned during the first three years.